59 



ancc and limited to iMiioxious numbors by natural onomios, no better 

 example could be cited than is all'orded by this plant-louse. Its 

 natural enemies include several species of ladybirds or '• ladybu^s," 

 syrphus flicks, aphis lions, the larva' of lacc-win<^ flies, numerous 

 species of minute hymenopterous parasites, and a parasitic funy;us. 

 The insect enemies are most ett'ective in destroying the plant-lice in 

 dry and Avarni weathei-. In a cool, dam}) atmos[)li(M-e, which is apt to 

 be encountered early in the season when plants are lirst set out, the 

 insect enemies are as a rule less active, and at such times injury by 

 plant-lice is likely to ])e most severe. 



The species shown in figure 58, known as the convergent ladj'bird 

 {Ilippodarnia corwerg mis)^ is one of the most beneficial insects, as it is 



Fio. TiS. — JlipjKxldiuia cimverr/cnx: a, iitliilt; h, pupa; r, liirvii — nil uiucli oiilnrKi'd (original, Division of 



Kiitornology). 



a most active destroyer of plant-lice which fi^ed on vegetables. It 

 is common on sugar beets, and it is interesting to note tluit on one 

 occasion it was reported as f(!eding on the leaves of that plant in 

 Oregon (Bui. 26, o. s., Div. Ent., p. 11). 



MKTIIODS OF <:()NT]lOI>. 



The melon louse, although a dillicult insect to treat when it occurs 

 on cucuirbits and some other plants, can be more readily (controlled on 

 beets. In fact, all of the leaf-infesting plant-lice can be destroyed on 

 beets by means of sprays and other washes and l)y some of the ordi- 

 nary general methods of farm piactice. 



Kerosene emulsion. — The standard remedy for pla)it-lice is kcrosene- 

 soiip emidsion, made by (•om])ining 2 gallons of kerosene, half a pound 

 of whale-oil or lish-oil soap or 1 quart of soft soap, with 1 gallon of 

 water. 



In preparing this emulsion the soap is first dissolved in boiling 

 water and then poured while; boiling hot, but awa}^ from the tire, into 

 th<j kerosene. The mixture is th<ni churned somewhat violently for 

 about five minutes by means of a force pump and direct discharge 



